Boy Mow Chau's answer to Sophie's Secondary 4 A Maths Singapore question.
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the confusing thing about this question is that it uses ‘r’ to represent the increase in radius from base radius of 350 ft ('r' is not radius of cavern!)
to avoid confusion, we have to use a different letter ‘R’ to represent the radius of the spherical cavern.
for rate of change of surface area, can also consider as
dA/dt = (dA/dR) x (dR/dt), since we already know dR/dt from the first part.
note that for dA/dV, it is easier to consider as ...
dA/dV = (dA/dR)/(dV/dR), rather than to try to express A in terms of V, then differentiate A with respect to V!
please do check for calculation errors.
to avoid confusion, we have to use a different letter ‘R’ to represent the radius of the spherical cavern.
for rate of change of surface area, can also consider as
dA/dt = (dA/dR) x (dR/dt), since we already know dR/dt from the first part.
note that for dA/dV, it is easier to consider as ...
dA/dV = (dA/dR)/(dV/dR), rather than to try to express A in terms of V, then differentiate A with respect to V!
please do check for calculation errors.
Date Posted:
1 year ago
Okie will do thank you!!
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